#1
Does anyone know of any songs that specifically use the C7 chord? I just started playing again last week and find it's a lot more fun to improve chords by playing actual songs, but I've looked through probably 100 tabs now and NONE of them seem to use the C7 chord.
#2
If I recall correctly Amazing Grace has a C7 somewhere in it.
When I'm Sixty-Four by the Beatles (maybe?)

When I was learning banjo almost every song I learned had a dominant 7th. If you don't mind old bluegrass/gospel then you can try some of them. C7 resolves to F so try Googling "gospel songs in the key of F" or something like that.
#4
Thanks for the recommendations. It's interesting to know that a lot of bluegrass/gospel music uses them too. I'll have to keep that in mind as I learn more dominant 7th chords.